The present invention relates to a lifting apparatus with a platform which can be raised and lowered.
Conventionally, lifting apparatus hydraulically driven to elevate a platform with workers and materials mounted thereon have been used for working in an elevated position, such as for painting, working in high places during building, installing phone lines or a signboard. A typical conventional lifting apparatus is comprised of a platform supported on a link-mechanism of the pantograph type which is expanded and retracted by a hydraulic cylinder to raise and lower the platform. In this case, one end of the hydraulic cylinder is connected to a support disposed below the cylinder, the other end being connected to an intermediate portion of a link lever of the link-mechanism, so that the hydraulic cylinder is actuated in an inclined position. However, in such a construction, the force of cylinder is not fully used for expanding the link-mechanism of pantograph type, that is, the apparatus is operated at an extremely low efficiency.
In order to obtain a high efficient force from the hydraulic cylinder, the hydraulic cylinder should be disposed so that the direction of the expansion coincides with the direction of the raising and the lowering of the link-mechanism of the pantograph type. To accomplish this, an improved lifting apparatus has a construction wherein the expansion of a hydraulic cylinder is directly transmitted to the link lever, by the connection of both ends of hydraulic cylinder with the link levers by any suitable means, such as arms. However, in this lifting apparatus, the connection of hydraulic cylinder with the link lever becomes mechanically complicated, and further since a multistage hydraulic cylinder must be provided in order to elevate the platform on the link-mechanism of the pantograph type to a high position the resulting apparatus is quite expensive.
The object of the present invention is to overcome such problems and to provide a lifting apparatus with driving means comprising a hydraulic cylinder and a flexible connecting member such as chain, wire, so that a simple construction of a lifting apparatus furnishes a greater expansion of the link-mechanism for the total cylinder stroke and the retracted length of the cylinder.
With the above and other objects and advantages in view, the present invention will become more clearly understood in connection with the detailed description of preferred embodiments, when considered with the accompanying drawings, of which: